Asynchronous Transfer Mode ("ATM") is an emerging packet switching network technology designed to provide service for a wide variety of applications such as voice, video and data. Originally proposed for use in the Broadband Integrated Services Digital Network ("B-ISDN") by the International Telegraph and Telephone Consultative Committee ("CCITT"), now reorganized as the Telecommunications Standardization Sector of the International Telecommunication Union ("ITU-T"), ATM is presently moving beyond the wide area network setting into the private network arena as a platform for local area networks ("LANs") with multimedia capabilities. ATM is now well known in the art and is described in various references. E.g., Martin de Prycker, Asynchronous Transfer Mode: Solution for Broadband ISDN (2nd Ed., Ellis Horwood Ltd., West Sussex, England, 1993).
In an ATM network, as defined by the CCITT standards, information is carried in packets of fixed size, specified for B-ISDN as 53 bytes or octets, called cells. These cells are individually labelled by addressing information contained in the first 5 bytes (octets) of each cell. Although ATM evolved from Time Division Multiplexing concepts, cells from multiple sources are statistically multiplexed into a single transmission facility. Cells are identified by the contents of their headers rather than by their time position in the multiplexed stream. A single ATM transmission facility may carry hundreds of thousands of ATM cells per second originating from a multiplicity of sources and travelling to a multiplicity of destinations.
ATM is a connection-oriented technology. Rather than broadcasting cells onto a shared wire or fiber for all network members to receive, a specific routing path through the network, called a virtual circuit, is set up between two end nodes before any data is transmitted. Cells identified with a particular virtual circuit are delivered to only those nodes on that virtual circuit.
The backbone of an ATM network consists of switching devices capable of handling the high-speed ATM cell streams. The switching components of these devices, commonly referred to as the switch fabric, perform the switching function required to implement a virtual circuit by receiving ATM cells from an input port, analyzing the information in the header of the incoming cells in real-time, and routing them to the appropriate destination port.
The deterministic nature of ATM makes it ideally suited for carrying multimedia or other real-time information, creating the opportunity to interconnect a wide variety of devices or equipment which generate or employ such information. For instance, an array of video surveillance cameras or motion sensors in an office building could be interconnected via an ATM network to efficiently deliver video images and other data to a common security control point. Further applications consist of the control and monitoring of devices in a residential or commercial setting. An individual may wish to program and/or monitor a microwave, refrigerator, clock, climate control, VCR, coffee maker, alarms, or other devices from one location in the home or at a remote location. A computer, either in the home or at a remote location, could use information from such devices to compile and transmit a shopping list, call a service specialist for the repair of a malfunctioning device, alert police to a security breach, or simply inform the homeowner of anything unusual or interesting.
Unfortunately, the current interfaces required for connection to ATM networks make the use of these networks with such simple peripherals prohibitively expensive. The major problem lies with current ATM protocols which require that the switches and end stations support vast quantities of signalling and management software, including a base set consisting of Q.2931, SSCOP, and SNMP. For a large class of possible simple ATM devices, such as those described above, the memory and processors required to implement these protocols is more expensive than the sum of the cost of the actual data handling components. Conceivably, lightweight versions of these protocols could be developed which would reduce the processing power necessary to implement an ATM interface for a simple device. However, even these protocols would require a minimum of software support which would be too costly for a large class of applications. Indeed, many devices could not be cost-effectively integrated into an ATM network unless fully-hardware interfaces could be employed. Furthermore, even if the necessity for this software support could be eliminated, the buffering in current ATM interfaces, in itself, could be prohibitively expensive.
Therefore, there exists a need for a mechanism to connect a number of simple peripherals to an ATM network using low-cost interfaces. Such interfaces would permit these devices to transmit and receive standard ATM cells without significant buffering, and without need to support current ATM protocols.